The processes for preparing chloromelamines disclosed in literature (see U.S. Pat. No. 2,472,361; British Pat. No. 931,747 and USSR Pat. No. 143,382) only describe reactions in an aqueous phase between melamines and chlorine or melamines and hexachloromelamine; a major drawback resides in the difficult drying of the resulting product which retains, even after centrifugation, considerable amounts of water, which results in the formation of crumbs which are difficult to pulverize. Another serious drawback is the chemical aggressivity of the reaction medium (with HCl and HClO present), which makes it necessary to use expensive, highly corrosion resistant materials, not only in the reaction section, but also in the subsequent sections of the plant (filtering and drying). The Applicant has now developed a very simple and practical method, which fully eliminates the abovesaid drawbacks.